Suppression of the parasitic buffer layer conductance in InSb/AlxIn1−xSb heterostructures using a wide-band-gap barrier layer

Abstract

InSb/Al x In 1-x Sb heterostructures display intrinsic parallel conduction in the buffer layer at room temperature that limits exploitation of the high-mobility two-dimensional electron gas (2DEG), particularly for nanostructured devices where deep isolation etch processing is impractical. Here, we demonstrate a strategy to reduce the parasitic conduction by the insertion of a pseudomorphic barrier layer of wide-band-gap alloy below the QW. We have studied the high-field magnetotransport in two types of InSb/Al x In 1-x Sb modulation doped quantum well heterostructures with and without the barrier layer in the temperature range 2-290 K and magnetic fields to 7.5 T. The conduction in the doping layer, the 2DEG, and the buffer layer are analyzed using a multi-carrier model that successfully captures the field dependence of the Hall resistance over the experimental field range. Samples with the barrier layer show significantly reduced buffer layer conduction compared to samples without. Our results are expected to be of importance for ambient temperature nano-electronic operation.

Multifunctional semiconductor micro-Hall devices for magnetic, electric, and photo-detection

“…Cr/Au Ohmic contacts to the InSb 2DEG were formed using a subtractive etch technique. 17 Here, we focus on the results from a w ¼ 2 lm Hall cross structure (SPVM and SGM data from a 1 lm and 4 lm device are presented in the supplementary material 18 ). The RT electrical transport properties of the devices are characterised by an electron density n 0 ¼ 5 Â 10 11 cm…”

“…Further details of the layer structure are given elsewhere. 17 Micro-Hall cross structures with lateral dimensions (w) varying between 1 lm and 4 lm were fabricated using e-beam lithography and shallow (%150 nm etch depth) reactive ion etching in a CH 4 /H 2 gas mixture. Cr/Au Ohmic contacts to the InSb 2DEG were formed using a subtractive etch technique.…”

Room temperature ballistic transport in InSb quantum well nanodevices

“…Considerable advantages would be afforded by pursuing such device concepts in this system; however, to-date, the RT operation of InSb QW nanodevices has been inhibited by excessive buffer layer leakage currents. 7 In this letter, we report the magnetotransport properties of mesoscopic devices fabricated on an InSb/AlInSb QW with a partitioned buffer layer (PBL) scheme 8 designed to suppress the parasitic leakage currents, which demonstrate remarkably clear ballistic transport at 295 K as a result.…”

“…The sample used is a 15-nm modulation doped InSb/ Al x In 1Àx Sb QW grown by MBE onto a GaAs (001) substrate with a PBL scheme (growth details are found elsewhere 8 ). A 15-nm pseudomorphic Al 0.3 In 0.7 Sb layer is incorporated 300 nm below the QW to provide a potential barrier to electrons and holes, thermally generated in the bulk of the buffer layer, from diffusing to the ohmic contact region.…”

“…The electron density and mobility of the QW at 295 K are n e ¼ 7.31 Â 10 11 cm À2 and l e ¼ 41 500 cm 2 /Vs (l 0 ¼ 586 nm), as deduced from high magnetic field measurements on 40-lm-wide (reference) Hall bridges. 8 Mesoscopic cross structures of various sizes were fabricated using e-beam and optical lithography and shallow (100 nm etch depth) reactive ion etching (RIE) in a CH 4 /H 2 (1:8) gas mixture. Magnetotransport measurements were performed in perpendicular magnetic fields (B) up to 7.5 T at various temperatures using standard AC and DC measurement techniques.…”